1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to generating a stereoscopic image bitstream, and more particularly, to generating a stereoscopic image format in a block unit and recording the stereoscopic image format in a stereoscopic image bitstream in order to efficiently compress or transmit a stereoscopic image formed of a base view image and an additional view image, and a structure of the stereoscopic image bitstream.
2. Description of the Related Art
Various methods of transmitting stereoscopic images exist. For example, standards such as MPEG-2 Multi-view Video Profile (MVP), a depth map transmitting method using MPEG-4 Multiple Auxiliary Component (MAC), and Multi-view Video Coding (MVC) of MPEG-4 AVC/H.264 have been established for efficient transmission of stereoscopic images.
However, such standards lack compatibility with a conventional two-dimensional (2-D) codec, and thus when a stereoscopic image is transmitted using the above-described standards, a user using a conventional 2-D reproducer cannot restore the stereoscopic image by decoding received data. Also, it is difficult to transmit 3-D images with the above-described standards, due to low channel capacity.
Accordingly, a method of combining a stereoscopic image into one image format and transmitting the image format has been developed. Representative examples of such a method include a side-by-side method and a top down method. In the side-by-side method, for example, the numbers of pixels in a row direction of a left image and a right image are reduced by half, respectively, and the reduced left and right images are respectively arranged as left and right sides of one combined image. In the top down method, for example, the numbers of pixels in a column direction of a left image and a right image are reduced by half, respectively, and the reduced left and right images are respectively arranged as the top and bottom of one combined image.
However, the resolution of the combined image as described above is reduced to half the resolution of the original image while reducing the number of pixels. Consequently in a conventional 2-D reproducer, a viewer may feel uncomfortable with the combined image, since the halves of the left and right images are shown. Also, when compressing or transmitting the combined image, compression efficiency deteriorates since correlation of left and right images are not considered.
A method of forming a single image format by combining left and right images in a pixel unit also exists.
FIG. 1A is a diagram illustrating a stereoscopic image format in a pixel unit for transmitting a stereoscopic image.
Pixels of a left view image and a right view image are sampled in a lattice unit, a right image is moved by one pixel in such a way that a left image and the right image are not overlapped, and then the right image is sampled. Accordingly, a single image format for a stereoscopic image is formed. A conventional 2-D encoder and decoder are used to transmit/receive the stereoscopic image. Since the left image and right image are formed as one stereoscopic image format having the same resolution, some pixels of the stereoscopic image format are lost.
FIG. 1B is a diagram illustrating an apparatus for restoring lost pixels of a stereoscopic image format in pixel units.
In order for a display device to reproduce an image in its original resolution, the lost pixels should be restored while generating the stereoscopic image format of FIG. 1A. Accordingly, values of an image sampled in a pixel unit are extracted in a direction, each directional pixel value is multiplied by a predetermined weight, and then the directional pixel values are all added in order to restore the original left and right images.
A stereoscopic image transmitting method includes an image format technology forming left and right images in field units.
FIG. 2A is a diagram illustrating a stereoscopic image format in field units. In FIG. 2A, input left and right images are vertically arranged each in one line and then are formatted to a sequential field unit. Then, the left and right images are transmitted and received.
FIG. 2B is a block diagram of a transmitting unit and a receiving unit of a stereoscopic image format in field units.
Referring to FIG. 2B, the transmitting unit and receiving unit includes a pre-processor 201 and a post-processor 211. The pre-processor forms and encodes a stereoscopic image format, and the post-processor restores a stereoscopic image by decoding the stereoscopic image format. Left and right images converted to pixel units are compressed by an MPEG encoder 202. Since MPEG, excluding MPEG-1, supports a compressing method of pixel units, MPEG has a structure that maintains compression efficiency while performing DCT in block units, and motion estimation and variation estimation.
According to the stereoscopic image format technology of FIG. 1A, left and right images are combined in a pixel unit in order to form a single stereoscopic image format. Accordingly, correlation between pixels is low, and thus performance of a DCT encoder according to an image standard, such as JPEG, MPEG, or H.26X, deteriorates, and compression efficiency decreases. Also, conventional stereoscopic image format technology including the stereoscopic image formats of FIGS. 1A and 2A does not define a pre-processor or a post-processor of a stereoscopic image. Accordingly, when the stereoscopic image format is decoded, left and right images are alternatively displayed in field units, and thus a serious flickering effect may be experienced by a user.